Patent GB-803667-A (GB)
Title: Improvements in or relating to control for change-speed transmission
IPC: F16H59/30
Filed: 1955-09-15
Abstract: 803,667. Change-speed gear. BORGWARNER CORPORATION. Sept. 15, 1955 [Oct. 14, 1954], No. 26427/55. Class 80 (2). In an automatic variable-speed transmission for a vehicle, wherein one of the factors controlling the fluid pressure applied either to a shift-valve or to a friction-engaging power-train completing device (to both as shown) is the accelerator pedal, the usual mechanical linkage between the floor-mounted accelerator pedal 568, Fig. 2, and the relatively-movable transmission-mounted member 167 which it controls, is replaced by a transmission-mounted diaphragm 538 responsive to engine-manifold depression through a conduit 584, which communicates through different-sized calibrated orifices 586, 588, respectively, with the manifold itself and with a point or circumferentially elongated zone which lies in the carburetter choke just below the usual throttle butterfly 570 when the latter is closed. This double vacuum communication gives the diaphragm rod 551 a movement closely similar to that of the accelerator pedal 568, independent of engine speed, and with a well-defined cut-in point. General.-Apart from the addition of a front brake pressure regulator valve 175, and the substitution of the vacuum control referred to above, both the gear and the control system are substantially the same as those in Specification 704,787. Function summary.-A compound planet gear, driven always wholly through a torque converter 30 of the over-run reactor type, provides two reduced ratios, direct-drive, neutral and reverse, by two band-brakes 33, 34 and two disc clutches 31, 32, all under fluid-pressure control. A manual valve 164 provides reverse, neutral, high and low range (RNHL) in that order. H gives starts in second with automatic shift to and from high in response to outputspeed- and engine-throttle-variable (" TV ") fluid-pressures acting in opposition on a 2-3 shift valve 166. L enforces first below a predetermined critical vehicle speed determined by a low-inhibitor valve 174, and second above that speed. Accelerator 3-2 kickdownshift is by solenoid action on the diaphragm-rod 551. Speed- and throttle-controlled torque overlap is provided for shifts between first and second ratios, whilst 3-2 downshifts have a throttlecontrolled timer valve 173 giving a free period for engine acceleration. Servo pressure is increased with throttle opening and decreased with speed, except in reverse when the speed factor is absent, and is augmented in low range and reverse. Engaging pressure of the front and rear brakes 33, 34 is subject to additional throttle control to give greater reduction at low throttle openings for smooth shifts. Gear arrangement.-Intermeshed planets 60, 61 mesh suns 56, 55 selectively clutchable by clutches 32, 31 respectively to a converterdriven input shaft 27, the planets 60 also meshing a ring-gear 35 fast on a final output shaft 26. First speed is by driving the smaller sun 55 through the front clutch 31 and holding the planet-carrier by a rear brake 34. Second is with the clutch 31 still engaged, together with a front brake 33 for the larger sun 56. Third direct-drive, is by engaging both front and rear clutches 31, 32 to drive both suns. Reverse is by engaging the rear clutch 32 and rear brake 34. Clutches and brakes.-The front clutch 31 is engaged by an annular piston 71 acting through a diaphragm-spring lever 73. The rear brake 34 (low and reverse) is engaged by fluid pressure 450 supplied to the upper face only of a piston 113. A spring 115 alone disengages. This brake is not self-tightening to forward-drive torque-reaction but is self-tightening to that for reverse drive. The front brake 33 (second ratio) is engaged by fluid pressure 526 supplied to the left face of a piston 98, and is disengaged in low range by a spring 99 alone, on exhausting pressure 526, and in high range by supplying disengaging fluid pressure 481 to the right face of the piston without exhausting the apply pressure 526. This brake is self-tightening to forward-drive torque-reaction. Fluid supply.-Input and output driven pumps 160, 161 supply the system under control of primary and secondary regulator valves 162, 163, the latter controlling only torque-converter pressure. Check-valves 220, 225 close to that pump producing the lower pressure. At takeover point of the output pump 161, when the input pump check-valve 225 closes, the output pump 161 relieves at a slightly higher pressure to a torque-converter feed-line 217, and the input pump now feeds only that line. A spill port 238 from the secondary regulator 163 feeds a gear lubricating line. Fluid system components.-In addition to the above are the following. A manual RNHL selector valve 164; an output-driven centrifugal valve 165 providing speed-responsive governor pressure 290; a " TV " valve 168, loaded through a spring 165 by the acceleratorresponsive diaphragm 538, Fig. 2, acting through a rod 551, lever 554, rod 551 and a kickdown 3-2 valve 167, to supply " TV " (i.e. throttle-variable) pressure 332; a TV modulator valve 169 which modulates TV pressure 332 to a line 387 in which the modulated TV pressure is the same as TV pressure itself up to a maximum of 22 p.s.i. at quarter throttle above which it remains constant; a compensatorvalve 170, subject to opposing governor and modulated TV pressures 290, 387, to regulate line pressure to a compensator pressure 419, which increases with output speed and decreases with increase in modulated TV pressure (i.e. with increased throttle opening up to quarter throttle), and is used to load both main pressure regulator valves 162, 163 in the pressure-reducing direction whereby servo line pressure 216 reduces with speed and increases with throttle opening (minimum line pressure at high speed, closed throttle is 75 p.s.i.; torque-converter pressure 30 p.s.i.); a TV-responsive low regulator valve 171 which regulates rear brake pressure 450 to less than line pressure with closed throttle for a smooth manual H-L shift; a TV- responsive front brake regulator valve 175 (not present in Specification 704,787) for regulating front brake pressure to considerably less than line pressure at closed throttle for smooth shifts into second ratio; a 1-2 valve 172 which, assisted by the low regulator valve 171, provides a torque overlap between rear and front brake engagement in manual shifts between first and second ratios, such overlap being line-pressure responsive and hence greater with increased accelerator depression and shorter with increased output speed; a 2-3 shift valve 166 producing automatic shifts between second and third ratios under opposing governor pressure 290 and TV pressure 332, further regulated to a lesser value by a TV regulator valve 292; a TV-responsive 3-2 timer valve 173 for restricting the exhaust of front brake release pressure 481 during released throttle 3-2 downshift to allow engine accelerating time; and a governor-responsive low inhibitor valve 174 for preventing engagement of low ratio above a predetermined output speed. Operation.-Neutral. With the engine running, input pump pressure 183, regulated at 203 in the primary regulator valve 162 to spill to the torque-converter feed line 217, feeds the system main 216, now blanked at the manual valve 164 and TV valve 168. The primary regulator valve 162 is loaded left by a spring 214 and right by line pressure 216 acting at 199 and by compensator pressure 419, 218. At standstill neutral, with idling engine, TV and governor pressures 332, 290 are both zero and the compensator valve 170 is spring-moved left to cause compensator pressure 419 to equal line pressure 216, 418. Under these conditions the loading- spring 214 of the primary regulator 162 maintains a minimum line pressure 216 of 75 p.s.i., and the torque converter feed-line 217 is similarly regulated to a minimum of 30 p.s.i. by the secondary regulator 163, which also regulates the torque-converter exhaust line 250 to exhaust 253 for continuous flow. High range.-Moved one step right, to H, the manual valve 164 introduces high range for normal starting and operation. This opens line-pressure 216 to lines 83, 269, the latter, 269, of which is initially blanked by the 2-3 shift valve 166 now spring-loaded to its rightward, downshift, position. Line pressure in the line 83 directly engages the front clutch 31; feeds the governor valve 165 at 289; passes through a line 468 to the 1-2 valve 172, which it shifts to the right; and thence through a line 467 to the front-brake regulator valve 175, from which, regulated to a value considerably less than line pressure by delivery pressure loading at 514, it passes through a line 526 to the left face of the front brake piston 98 to engage the front brake 33. With front brake and clutch thus engaged the gear is in second ratio and the vehicle is started through the torque-converter by accelerating the engine. Accelerator depression, through the vacuum-operated linkage 555, now rightwardly loads the TV valve 168, metering TV pressure 332 which acts at 525 against the loading of the front-brake regulator valve 175 to permit rapid increase of front brake pressure 526 up to line pressure 467. TV pressure 332 also feeds the TV modulator valve 169 which applies modulated TV pressure 387 (TV up to a maximum at quarter throttle) to oppose the now acting governor pressure 290 in the compensator valve 170, the compensator pressure 419 metered by which varies inversely with accelerator depression and directly with output speed, and opposes at 218 the leftward loading of the primary and secondary regulator valves 162, 163, whereby line and converter pressures both increase with engine throttle opening (up to quarter throttle) and decrease with output speed. TV pressure 332 also passes to a TV regulator plug 292 of the 2-3 shift valve 166, which plug meters the TV pressure to a lower value into a passage 310, where it a